update sunxi-boards and sunxi-tools submodules

Signed-off-by: Jari Helaakoski <tekkuli@gmail.com>
update u-boot submodule and adapt to new falcon binary format

Signed-off-by: Jari Helaakoski <tekkuli@gmail.com>
update linux-sunxi submodule.

Use sunxi-3.4 now. Now a20 is also supported.

Signed-off-by: Jari Helaakoski <tekkuli@gmail.com>